The subject matter disclosed herein relates to the art of rotary wing aircraft and, more specifically to a torque converter for a rotary wing aircraft powered by a piston engine.
Some configurations of rotary wing aircraft, or rotorcraft, require the capability to allow for torque slip and freewheeling of the drive system, allowing the engine speed to be essentially independent of drive system speed to prevent stall or damage of the engine under certain operating conditions. These conditions include, but are not limited to, engine startup, increasing or decreasing drive system speed regardless of engine speed, stopping drive system output with the engine running, and autorotation maneuvers of the rotorcraft. Turbine engine powered rotorcraft typically do not require additional components to allow for torque slip as the turbine engine design inherently includes a torque slip capability. A freewheel unit is still necessary to allow for autorotation and engine shut down.
Piston engine powered rotorcraft require both additional torque slip and freewheel devices for operation. Typically, such rotorcraft utilize belt drives, which are effective at low power levels, but eventual wear requires regular inspection and replacement of the belts. Larger rotorcraft, operating at higher power levels, have used wet clutches with friction discs to allow for torque slip, but these configurations are prone to overheating and wear.